Apparatus for automatic balancing of rotating bodies



2,659,243 APPARATUS FOR AUTOMATIC BALANCING OF ROTATING BODIES FiledJune 27, 1952 G. DARRIEUS Nov. 17, 1953 3 Sheets-Sheet vJ.

IN VEN TOR Nov. 17, 1953 G. DARRlEyS 2,659,243

APPARATUS FOR AUTOMATIC BALANCING 0F ROTATING BODIES Filed June 27, 1952s Sheets-Sheet 2 INVENTOR" I \z i I I30 j Z g P ATTORNEYS Nov. 17, 1953G. DARRIEUS APPARATUS FOR AUTOMATIC BALANCING 0F ROTATING BODIES sSheets-Sheet 3 Filed June 27, 1952 IIIIIIIIIII III M z/zllll INVENTOR BY/P JV2% M w ATTORNEYJ Patented Nov. 17, 1953 APPARATUS FORAUTOMATICBALANCING OF ROTATING BODIES Georges Darrieus, Houilles, France,assignor to Aktiengesellschaft Brown,

Boveri & Cie.,

Baden, Switzerland, a joint-stock company Application June 27, 1952,Serial No. 296,023 Claims priority, application France July 5, 1951 14Claims. 1

The present invention relates to'apparatus for static and dynamicbalancing of rotary machine parts and particularly to those classes of"machines such as for example, centrifuges, grinding machines andturbomachines not stationarily operated, and the like wherein operatingconditions involve unpredictable displacement of the rotating masses.

Because of the unpredictable nature of the imbalance, the balancingsystems have to be designed in such manner that the imbalance will becompensated out in an automatic manner whenever and at whatever place orplaces it may occur.

Among the systems already proposed to effect this result are those whichmake use of a plurality of balls positioned symmetrically about theshaft of the machine and which are so arranged as to be free formovement along an arcuate path concentric with the shaft. Rings ofsufficiently great mass placed on the shaft have also been employed toeffect automatic rebalance and operate on the same principle as theballs, that is to say by an automatic change in position along thearcuate path concentric with the shaft axis. Devices of these types arecapable of compensating every kind of imbalance both as to direction andmagnitude, but with respect to the latter, only within certain limitswhich depend upon the mass of the balls or rings.

Moreover, such devices are not without other inherent disadvantages. Forone thing they are applicable only in cases where the machine operatesat rotary speeds in excess of the critical speed. By critical speed ismeant that number of revolutions per unit of time which corresponds tothe natural or resonant frequency of the mass which is being rotated. Acondition for its being carried out therefore is a sufliciently flexibleinstallation of the rotating mass, whether permanently, as for examplein pendulum centrifuges with a suspended vessel, or temporarily, as ingrinding machines, in which the normal rigid installation of therotating mass is made more or less flexible in more or less quicklysucceeding units of time between the work periods whenever the necessityfor a new balancing arises.

Another disadvantage inherent in the prior art automatic rebalancers ofthe movable ball or roller type is an inability to respond fully .andaccurately to correct a condition of imbalance. This arises from thefact that the change in ball or roller position to bring about arebalance is made dependent only upon the very slight inclination of therolling path brought about by the,

imbalance. Consequently the presence of any roughness along the path orfriction can easily lower the response sensitivity of the balancer.

In accordance with the present invention, the

foregoing disadvantages are all eliminated and the inventive conceptwhich makes this possible resides in the novel use of revolving reactivecen trifugal forces in the bearings of the rotating member which arecreated by and vary in proportion to the magnitude of any imbalance inthe member. Such forces do not exist when the rotating member isperfectly balanced and consequently the magnitude of such reactive forcemay be taken as a measure of the imbalance to be compensated out.Moreover, as will become more apparent in a later part ofthisspecification, the improved balancer device can be used on rotarymembers regardless of the speed at which these members are operated.Thus it matters not that the member rotates below or above its criticalspeed and hence the invention permits substantially rigid installationsof the rotary members as distinguished from the previously discussed andmore undesirable flexible installations formerly necessary when therotary member was required to rotate at speeds higher than its criticalvelocity.

According to the invention, the revolving'reactive forces generated inthe bearings as a result of any imbalance bring about correspondingchanges in the pressure of the lubricating medium utilized in thebearing, and these pressure changes are then utilized to effect positiveand corresponding imbalance compensating changes in the positions of aplurality of symmetrically positioned balancing members such as balls orrollers arranged for displacement along an arcuate path concentric withthe shaft axis of the rotating member. The balancer is entirelyautomatic in character, has a very high order of response sensitivityand any imbalance is compensated out as soon as the slightest revolvingcentrifugal force of reaction occurs in the bearings.

In the accompanying drawings, several different embodiments of theinvention have been shown but these are to be viewed as typical ratherthan limitative of the structural-forms possible within the scope of theinventive concept defined in the appended claims.

With reference now to the. drawings:

Fig. 1 is a longitudinal view partly in central section at one endbearing portion of the shaft element of a rotary member containing theaxis of rotation illustrating in somewhat diagrammatic form oneembodiment of the invention -de-' signed for automatic rebalancing ofmembers which rotate at speeds below their critical angular velocity; v

Figure 2 is a transverse section through the 3 automatic balancerelement taken on line 22 of Fig. 1;

Fig. 3 is a transverse section on line 3-3 of Fig.1;

Fig. 4 is a view similar to Fig. 1 showing an embodiment of theinvention to be utilized when the rotary member to be balancedautomatically is to be driven at speeds in excess of its criticalangular velocity;

Fig. 5 is a view similar to Fig. 2 taken on line 5--5 of Fig. 4;

Fig. 6 is a longitudinal view partly in central section through theshaft element of a rotary body to be balanced automatically showing anembodiment of the invention to be used when the balancer elements cannotbe located near the end bearings of the shaft as in Figs. 1-5;

Fig. 7 is a transverse fragmentary view showing an alternativerefinement for the balancer construction shown in any of the previousviews by which the ball elements are maintained against displacementwhen the shaft is at rest;

Fig. 8 is another transverse view similar to Fig. '7 but taken in planenormal thereto;

Fig. 9 is a central longitudinal section similar to Fig, 1 showing amodified embodiment of the invention wherein servomotor means areemployed to translate pressure changes in the bearing reflective ofimbalance into corresponding displacements of the ball elements in thebalancer;

Figs. 10, 11 and 12 are transverse sections taken on lines iii-l0, H-Hand 12-12, respectively of Fig. 9;

Fig. 13 is a central longitudinal section simi lar to Fig. 1 showingstill a different embodiment of the invention suited particularly toconstructions wherein ball, roller, or other types of antifrictionbearings are employed for mounting the shaft ends; and

Fig. 14 is a central longitudinal section similar to Fig. 13illustrating another embodiment of the invention suitable for shaftsmounted in antifriction bearings.

Referring now more particularly to Figs. 1-3, numeral I designates oneend portion of the shaft element of a rotary member (not illustrated)and which is mounted in a stationary bearing sleeve ll. Lubrication forthe portion of shaft 10 within the bearing sleeve H is provided by athin film of oil i2 maintained therebetween and which is supplied to thesleeve in any conventional manner not shown. The automatic balancer iscomprised of a plurality of balancing masses in the form of rollingbodies such as the balls I311, l3b, (3c contained within a cylindricalbody member is made rotatable with the shaft. The halls are disposedsymmetrically about the shaft axis and are arranged for movement alongan arcuate rolling path concentric with the axis of shaft I0 and whichis constituted by an annular space provided in the body 14, and which isdivided circumferentially into three separate sections lia, [b, |5c eachcontaining one of the balls by means of identical arcuate inserts 16a,1522, Vic circular in transverse section and'which are so arranged thatthe three space sections I511, 15b, 150 are of equal length.

Insert 15a is provided with a longitudinal bore Ha extending from oneend to the other so as to communicate with the spaces or chambers 15a,15b, adjacent such ends and a transverse bore [841 extending radiallyinward from bore Ila, the bore 18a being in alignment and communicativewith a radially extending bore Na in the 4 body l4. At its innermostend, bore [Ba communicates with another bore 20a extendinglongitudinally through the body l4 and shaft l0 in the direction ofbearing sleeve I l. Bore 20a in turn communicates with a pair ofradially arranged, axially displaced bores 21a extending radiallyoutward in the shaft to that portion of the surface of the latter whichis situated within the bearing sleeve ll. Moreover, in this embodiment,which is adapted for use on apparatus designed to run at speeds belowits critical speed, it is'necessary that the bores 2la be in radialalignment and on the same side of the shaft as the bore I9a associatedtherewith since any revolving centrifugal force created in the shaft l0because of an overbalance will be directed toward the location of suchoverbalance.

In a similar manner, the two other arcuate inserts [6b, [6c are providedwith longitudinal bores I lb, l'lc, transverse bores I82), I80, andbores I91), I90 and 26b, 20c lead to other pairs of bores H19, 210 inthe shaft which are in radial alignment with and extend in the samedirection as their associated bores I917, 190. Being symmetricallydisposed, bores lBa, 18b and l8c are spaced 120 apart and the same istrue for the other radial bores described.

Assuming a condition of overbalance to exist in the rotating member, thepressure in the oil film external forces acting on the rotating body(for example its weight) and is fixed in its spatial direction, and asecond pressure component constant in time but variable along theperiphery,

which stems from the centrifugal force attributable to the overbalanceand which revolves at a velocity synchronous with that of the shaft In.The first pressure component, also of a frequency equal to that of theshaft rotation, does not enter into consideration because of theviscosity and inertia of the oil and of the balancing masses I3a-i3c.The constant component is however reflected by a change in pressure inthe oil film l2, the pressure being greatest in the plane and directionof the overbalance and smallest in the opposite direction. Thus underthe influence of these momentary differences in pressure, the boreswhose mouths lie in the general direction of the overbalance such asbores 21a for example, derive continuously from the oil film l2 of thebearing a little of the oil while the opposite bores 2|b, Me at the sideaway from the overbalance return a corresponding amount of oil to thefilm. The surface of the balls ltd-43c have a minimum running clearancewith the walls defining the annular chambers 55a, 45b, 15c and consequently the balls are displaced in their cha: bers by the oil in themanner of pistons. The direction and amplitude of the ball displacementwill automatically be such as to gradually com pensate for theoverbalance until the rotating member is once again in a state ofdynamic balance. Thus for example should the overbalance be in thedirection of the bores 2 la shown in Fig. 1, oil under pressure willflow through bores 28a, Isa, l-Sa, and Ila to chambers I511, I512causing displacement of the balls l3a, 53b therein in the directionindicated by the arrows away from the direction of overbalancej Becauseof the lower oil pressures at the mouths of bores 21b, 2|c oil displacedby movement of balls 13a, I31) is able to return to such bores from thechambers l5a,

I b through bores 11b, and 20b, 20c. Another balance organization likethat shown in Figs. 1-2 is arranged at the opposite end of the rotarybody adjacent the bearing at such end thus providing a complete staticand dynamic balance for the body.

In the embodiment shown in Figs. 1 and 2 and similar embodiments whichwill be later referred to wherein the pressure developed fordisplacement of the balls is limited to that developed only at the oilfilm in the bearing, it is of course quite possible that some oil mayleak out of the chambers [5a. I51), I50 when the rotatable body is atrest thus permitting the balls to shift their positions. This would bemost undesirable since upon restarting, the body would no longer bebalanced and a new balance would be delayed until the balls had movedthe necessary distance along their rolling path. To prevent the ballsfrom shifting their position while the rotatable body is not rotating,it will ordinarily be sufficient in the case of small diametered bodiesto make the mouths of the bores 2 let-2 I c so small that the capillaryforces counteract the hydrostatic pressures caused by the diiferences inthe heights of the oil levels in the bores and by the Weight of thebalancing masses.

For larger diametered rotatable bodies, positive means maybe employedfor locking the balancing masses against displacement. Thus in Fig. 1and Fig. 2 and other similar embodiments, it will be seen that springloaded, ball type check valves 22 are placed in each of the bores 13a, I9b and 190; The springs load the ball members of the check valves ina'radially inward direction and hence the valves will closeautomatically to block oil flow therethrough whenever the centrifugalforces developed by rotation of the body fall below the closing forcesof the springs.

A somewhat diiferent type of device for preventing displacement of theballs l3 when the rotatable body is at rest is shown in Figs. 7 and 8.In this embodiment, the ball lock consists of a braking device actingdirectly on the balls in the form of an elastic ring 23 interrupted toestablish a gap at 24 and which is disposed in a circular groove 25concentric with the bearing shaft axis in the body l4 of the balancer,the groove 25 being located at the radially outward side of the ballsI3. An abutment 26 separates the two ends of the ring 23 at the break24. The ring ends have adequate play with respect to the abutment so asto be able to open freely under the influence of centrifugal forcesdeveloped by rotation and the abutment insures positive rotation of thering 23 as the bodymember l4 rotates. When the body is at rest, splitring 23 will of course tend to move radially inward at all points alongits periphery until contact is established with the surface of the ballsl3 thus locking the latter against displacement since the ring 23 itselfcannot rotate relative to the body I 4. However, when body I4 isrotated, the centrifugal force acting radially outward at all pointsalong the periphery of ring 23 will exceed the inherent radially inwardforce of the ring causing the ring to expand and release its contactwith the ball surface. The balls are then free to take up a new positionof balance whenever the necessity arises.

Figs. 4 and 5 illustrate an embodiment of the invention used when thebody to be balanced is drivenat a frequency of rotation exceeding thenatural frequency of the body. 'In view of the similarity inconstruction to Figs. 1 and 2,'lik e componentsin the two embodimentshave been given the same reference numerals but with primes added to theembodiment of Figs. 3 and 4. When the frequency of rotation exceeds thenatural frequency of the body the revolving centrifugal force acting onthe shaft at the hearing has a direction diametrically opposite that ofthe overbalance. Hence. each of the radial bores |9a'l9c' is displacedaway from the bores 2la-2lc', respectively associated therewith.Otherwise the arrangement and operation are the same as in Figs. 1 and2.

As already explained, the complete static and dynamic balance requirestwo balancers of the type described situated in two different planes,for example in the vicinity of the shaft endseach of which is connectedas a rule with the nearest situated bearing pin. If, as an exception,the two planes of balancing have to be located at relatively greatdistances from the bearings such as is depicted in Fig. 6, it isadvantageous to provide each balancer with pressure oil not only fromthe bearing nearest thereto but also from the bearing supplying pressureoil to the other balancer. Accordingly the balancer 21 to the leftincludes three ball chambers as in Figs. 1 and 2 and with the three setsof radial bores 28 in the shaft leading to the oil film in bearing sleev29 in radial alignment with and on the same side of the shaft as thethree bores 39 in balancer body 21 leading to the ball chambers which isalso the arrangement of Figs. 1 and 2. The balancer 3| on the right isconstructed in the same manner as balancer 21 but displaced relativelythereto so that the three sets of radial bores 32 leading to the shaftbearing sleeve 33 are diametrically opposite the three sets of radialbores 23 at the opposite end of the shaft. It will also be noted thatthree bores 34 extend longitudinally through the rotor body andinterconnect the bores 35 and 30 and hence also the bores 28 and 32. Inthe interest of simplicity however only one of the three bores 34 hasbeen illustrated as is also the. case with respect to bores 28, 30, 32and 35. An adjustable valve represented diagrammatically as a screw 36is inserted in each of the bores 31 between bores 28 and 30 to regulateoil flow therethrough and other .valves 38 are similarly. inserted inbores 39 between bores 32 and 35.

With the arrangement thus described, .rebalancing of the body becomesmore rapid and moreover each balancer is maintained non-responsive tosuch unbalance as the other balancer is supposed to compensate. That isto say, an over.- balance occurring in the plane of one balancer, forexample, in the balancer 3| on the rightside produces no reaction in theother balancer 21 and vice versa. This can be explained in the followingmanner. If it be assumed that th unbalance to be compensated lies in theplane of balancer 3|, the rotating centrifugal force attributablethereto will result in an increase in oil pressure at the mouths ofbores 32 in bearing 33 and a decrease in oil pressure at the mouths ofbores 28 in bearing 29. The relative openings in the valves 36, 38 andthe drops in oil pressure which they establish in the communicatingbores 37, 34 and 39 are so regulated that the increased pressure at themouths of bores 32 and the reduced pressure at the mouths of bores 23develop a pressure gradient along the bores 39, 34, 3! such as willresult only in a continuous flow of oil from bores 32 towards bores 28without any diversion of oil into the bores 30 of the left balancer 21nor antenna displacement of the balancing balls therein The increasedoil pressure at bores 32 is however ac-.- companied by a flow of oilradially outward through bores 35 in the right balancer 3i and effectsthe necessary displacement of the balancing balls to compensate for the.unbalance.

In all embodiments so far described, displacement of the balancing ballsis efiected directly as a function of the oil quantityv removed from theoil film in the bearing sleeves and which passes directly to the annularspaces i5a-l5c. While this is a practical arrangement for certainapplications, it may be advisable in cases where the condition ofbalance is subject to sudden changes, such as in centrifuges, toinsertan oil servomotor into the system in order to efiect rebalancemore quickly. One practical arrangement of this kind is illustrated inFigs. 9-12.

From Fig. 10 it will be evident that the arrangement of the balls,inserts, spaces and bores in the balancer body is the same as in Figs.1-2 and hence corresponding elements have been assigned the samereference numerals but with double primes applied thereto in order todistinguish one from the other. However, the bores 2Ia"-2Ic" at thebearing I!" instead of being connected directly to bores 2lla-20c" as inFigs. 2 lead respectively to one end of the cylinder elements 42a, 42b,420 of pilot valves, the pistons of which are designated by numerals43a, 63b, 430. The opposite ends of the cylinders 4266-420 are allinterconnected by means of bores Mar-44c as shown in Fig. 12.

Pistons 4341-430 are connected respectively to pistons 45a, 45b, 450having longitudinal bores therethrough and which operate in cylinders45a, 46b, Mic. These latter are known as D valves and the position ofthe piston in the cylinder determines the amount of pressure oil whichwill be allowed to flow from the supply source to the balancer. Thepositions taken by the parts as shown in these views, and assumingrotation at a speed below the critical speed, are indicative of anincreased pressure in the oil film l2" at the mouth of bore 21a" and adecreased pressure at the mouths of bores 21!)", 2lc. Consequentlypiston 5311 has been moved to the right and pistons 43b, 430 to theleft, movement of the latter being produced by discharge of oil from theright end of cylinder 42a through bores 44a, 44b into the right end ofcylinders 42b, 42c. Piston 45a will likewise have moved to-the right andpistons 45b, 450 to the left. Oil under pressure from a suitable sourcecoming into the bearing through bore 41 is thus free to pass from thelatter into bore 2.0a", these two bores havin been placed incommunication by the annular re, case in piston 45a, and thence throughbore 19a" into one end of the balancing chambers a", 15b" to effect thenecessary repositioning of balls l3a, l3b" in the direction denoted bythe arrows. At the same time, oil will be returned from the other end ofchambers 15a", l5b" through bores !9b, I90", 251)" and 26c" intocylinders 46b, 46c and flow from the latter through the longitudinalbores in pistons 45b, 45c and thence into the outlet line 48 for thepressure oil. Thus in the embodiment shown in Figs. 9-42, the oilpressure available for actuating the balancing masses is that of theextraneous source and the pressure of the oil film at the bearing isused only to actuate the pilot valves which in turn control, in aproportional manner, the flow of oil into and out of the balancer fromthe source of greater pressure and also greater flow.

- "In all of the embodiments so far described, it has been assumed thatthe sleeve bearings U carry the entire weight of the rotating body.However, it may well be desirable to journal the shaft ends of. the bodyin anti-friction bearings such as those of the ball or roller type. inwhich event the body must be provided with other devices capable of.developing the change in oil pressure indicative of imbalance. Onesuitable arrangement for effecting the desired result is shown in Fig.13. In this view, the balancer is identical in man respects with thatshown in Figs. 4 and 5, and like parts have hence been assigned likereference numerals but with triple primes added for purposes ofdistinction. The shaft end 10" is supported by means of a ball bearing50. In order to .develop the necessary fluid pressures for actuating thebalancing masses, shaft in' has mounted thereon a false bearing sleeve51 having radially extending vanes 52 thereon. Oil under pressure issupplied from a suitable source through a longitudinal bore 53 into theinterior of shaft 18'' and thence passes radially outward through bore54 to develop an 011 film 55 between. the'shait surface and the surfaceof the bearing sleeve. When shaft 10 rotates, the resistance torotationpresented by the vanes 52 thus develops a slip between thebearing sleeve and shaft with the result that the sleeve 5i rotates inthe same direction as shaft ill but at a slower speed. Under theseconditions, distribution of the oil film 55 along the periphery of thesleeve 5| is uniform and any unbalance in the body will set up the sametype of pressure change in the film 55 as in the film 12 of theembodiment according to Figs. 1 and 2. If desired, the false bearingsleeve 5! can be maintained stationary but the arrangement il1uS- tratedis preferred since it reduces the losses in cident to liquid friction.It will be noted that as in Figs. 4 and 5, bore 2la' although radiallyaligned with bore l9a' extends in the opposite direction, this for thereason that the reaction of the false bearing sleeve 5| is now producedpredominately by the inertia instead of being of an elastic nature as inthe case of the Fig. 1 embodiment, or as it can become again beyond acertain criticalvelocity when the inertia is com,- pensated for by amore or less stiff return of the bearings by means of springs.v

Another practical embodiment of the invention when the rotatable body ismounted in antifriction bearings is shown in Fig. 14. As in previousembodiments corresponding components have been assigned like referencenumerals but with quadruple primes added. Numeral 56 designates the ballbearing supporting the shaft end l8"". The latter is provided with alongitudinal bore 51 extending inwardly from the end of the shaft to acylindrical recess 58 containing 2, cylindrical disk 59 the diameter ofwhich is slightly less than that of recess 58. The disk 59 has a minimumof lateral play in the recess 58 but yet is able to slip rotationallywith respect to the rotatable body. Disk 59 is provided with an axialportion 60 extending to the exterior of the shaft through bore 51 andfan blades 63 mounted thereon so as to develop a rotational slip betweenthe rotatable body and the disk 59. Oil under pressure is suppliedthrough longitudinal bore 61 in the axially extending portion 60 andthence through a radial bore 62 to the annular space between theperiphery of the disk 59 and that of the recess 58.

As long as the rotatable body remains balanced,

disk 59 remains centered with respect to the shaft axis and all ballchambers in the balancer will receive the same oil pressure. If howeveran overbalance should arise, the disk 59 will shift in the direction ofoverbalance thus raising the pressure of the oil film at the side of theoverbalance and causing the balancing balls to shift until dynamicbalance is restored.

The novel automatic balancing device which has been described is notlimited to use of a liquid of relative high viscosity, e. g. lubricatingoil. Other fluids such as water or air can be substituted for the oil,particularly in those embodiments wherein the rotatable body isjournalled in anti-friction bearings in which false bearings are usedand which do not require for the production of the requisite moderatepressures such exceptionally small clearances as is the case withbearings upon which loads are imposed.

I claim:

1. Apparatus for automatically balancing a body mounted for rotationabout its axis comprising a balancer member containing a plurality ofarcuate chambers positioned symmetrically and concentrically about theaxis of said body, each said chamber having a solid balancing masstherein movable along the arcuate path defined by the chamber, means fordeveloping fiuid pressure diiferentials about the axis of rotation ofsaid body proportional to any unbalance in said body, and means applyingsaid pressure differentials to said balancing masses at opposite sidesthereof in said chambers to effect displacement of said masses in adirection restorative of balance.

2. Apparatus for automatic balancing of a rotatable body as defined inclaim 1 and which further includes means responsive to centrifugal forcefor locking said balancing masses against displacement when said body isin a state of rest and unlocking said masses when said body is rotated.

3. Apparatus as defined in claim 2 wherein said locking means iscomprised of a check valve located in radial bores leading to saidchambers.

4. Apparatus as defined in claim 2 wherein said locking means iscomprised of a resilient split ring expandable and contractible torelease or engage respectively the surface of said balancing masses.

5. Apparatus for automatically balancing a body mounted for rotationabout its axis comprising a sleeve surrounding a shaft portion of thebody, means providing a fluid film between the sleeve and shaft, abalancer member containing a plurality of arcuate chambers positionedsymmetrically and concentrically about the axis of said body, each saidchamber having a solid balancing mass therein movable along the arcuatepath defined by the chamber, and means placing said chambers at thesides opposite the masses therein in communication respectively withsaid fluid film at difierent points about the film periphery whereby thepressure differentials effected around the periphery of the film as aresult of any unbalance in said body produce a compensating displacementof said balancing masses restoring said body to a balanced state.

6. Apparatus for automatically balancing a rotatable body as defined inclaim 5 wherein each chamber communicates with said fiuid film on thesame side of the body axis as lies said chamber.

7. Apparatus for automatically balancing a rotatable body as defined inclaim 5 wherein each chamber communicates with said fluid film on 10 theside of the body axis opposite to that on which the chamber lies.

8. Apparatus for automatically balancing a rotatable body as defined inclaim 5 including a balancer of the type defined associated with theshaft at each end of the body and wherein the respective fiuid films arein communication with each other.

9. Apparatus for automatically balancing a rotatable body as defined inclaim 5 wherein said body is journalled in anti-friction bearings andsaid sleeve constitutes a false bearing.

10. Apparatus for automatically balancing a rotatable body as defined inclaim 9 wherein said sleeve is provided with vanes to effect aiotlational slip between the sleeve and rotatable 11. Apparatus forautomatically balancing a rotatable body mounted for rotation about itsaxis comprising a sleeve surrounding a shaft portion of the body, meansproviding a fluid film between said sleeve and shaft, a balancer membercontaining a plurality of arcuate chambers positioned symmetrically andconcentrically about the axis of said body, each said chamber having asolid balancing mass therein movable along the arcuate path defined bythe chamber, and servo motor means controlling flow of a fluid underpressure to said chambers, said servo motor means being responsive toand controlled by pressure variations effected at difierent points aboutthe periphery in said fluid film as a result of any unbalance in saidbody.

12. Apparatus for automatically balancing a rotatable body mounted byanti-friction bearings for rotation about its axis comprising a balancermember containing a plurality of arcuate chambers positionedsymmetrically and concentrically about the axis of said body, each saidchamber having a solid balancing mass therein movable along the arcuatepath defined by the chamber, means providing a cylindrical recessconcentric with the axis of said body, a cylindrical disk in saidrecess, said disk having a diameter slightly less than that of saidrecess, and being rotatable relative to said body, means maintaining afilm of fluid between the periphery of said disk and said recess, andmeans placing said chambers at the sides opposite the masses therein incommunication respectively with said fluid film at different pointsabout the circumference of said cylindrical recess.

13. Apparatus for automatically balancing a rotatable body as defined inclaim 12 wherein said fiuid film is supplied from a source underpressure.

14. Apparatus for automatically balancing a rotatable body as defined inclaim 12 wherein said disk includes an axial portion extending to theexterior of said body, said axial portion being provided with vanes toeffect a rotational slip between said disk and body.

GEORGES DARRIEUS.

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